Biomedical subjects

D Vitacco

Publications and source records attributed to D Vitacco.

3 recordsLinked to original sources

PubMed1999

Visual processing in infants and children studied using functional MRI.

We studied the development of visual processing in 58 children, ranging from 1 d to 12 y of age (median age 29 mo), using functional magnetic resonance imaging. All but nine children had either been sedated using chloral hydrate (n = 12) or pentobarbital (n = 28). Nine children were studied under a full halothane/ N2O:O2 anesthesia. In the first postnatal month, 30% of the neonates showed a positive blood oxygenation level-dependent (BOLD) contrast signal, whereas, for infants between the ages of 1 mo and 1 y, 27% did so. Thirty-one percent of children between 1 and 6 y of age and 71% of children aged 6 y and above showed a positive BOLD contrast signal change to our visual stimulation paradigm. Besides the usual positive BOLD contrast signal change, we also noted that a large portion of the children measured displayed a negative BOLD contrast signal change. This negative BOLD contrast signal change was observed in 30% of children up to 1 mo of age, in 27% between 1 mo and 1 y of age, in 47% between 1 and 6 y of age, and in 14% of children 6 y and older. In the children in which we observed a negative correlating BOLD contrast signal change, the locus was more anterior and more lateral than the positive BOLD contrast signal, placing it in the secondary visual cortical area. The results indicate that when using functional magnetic resonance imaging on children, the primary visual cortical area does not respond functionally in the same manner as that of the adult until 1.5 y of age. This supports earlier clinical and electrophysiologic findings that different cortical mechanisms seem to contribute to visual perception at different times postnatally.

Adult↗

PubMed1998

Neuroelectric mapping reveals precursor of stop failures in children with attention deficits.

Children with attention deficit disorders (ADD) may have specific problems with response inhibition in the STOP task. This task requires that subjects stop responses to a primary task if a second signal follows. However, it is unclear whether these problems reflect an impairment of the stopping process per se, whether they are related to reduced frontal lobe activation and whether they are confined to severe and pervasive forms of ADD. In 11 ADD and nine control children, 32 channel event-related EEG potentials (ERPs) were recorded in a STOP and a delayed GO task. Mapping revealed that both tasks evoked a similar sequence of neuroelectric microstates, i.e. of time segments with stable map topography. Adaptive segmentation identified the transition between these microstates. Reliable group differences were found in several microstates and in both tasks despite matched performance. In the GO task, ADD children had topographically altered P2/N2 microstates and attenuated P300-type microstates. In the STOP task, a topographically altered N1 microstate which coincided with the onset of the stop signal preceded the stop failures of ADD children. The timing of this microstate is too early to reflect deficits in actual stop signal processing and instead suggests altered initial orienting of attention to the primary signal in ADD children. Imaging with low resolution tomography (LORETA) during this microstate to stop failures indicated mainly posterior activation for both groups and increased rather than reduced frontal activation in ADD children. For a later microstate (P550), LORETA indicated strong frontal activation after successful stopping, but no group differences. The results suggest that information processing of ADD children deviates during activation of posterior mechanisms which may be related to the orienting of attention and which precedes and partly determines inhibitory control problems in ADD.

Arousal↗

PubMed1994

Mapping brain electric micro-states in dyslexic children during reading.

An important issue in current research on dyslexia is to what extent the reading deficits of dyslexic children are related to processing deficits at the sensory-visual level, at the cognitive-linguistic level or at both levels. Event-related potential mapping distinguishes the split-second processing stages during reading as brief brain-electric micro-states and can address this issue directly. Previously, conventional studies have yielded inconsistent patterns of event-related potential differences between dyslexic and control children, but most of these discrepancies could result from the widely differing methodologies. We used event-related potential mapping during silent reading of correct and incorrect sentence endings to examine the neurophysiology of sensory and cognitive processes in dyslexic and control children (n = 12/group). Selected findings from spatio-temporal analyses of map strength (global field power), map latency and map topography measured in three dimensions are presented. Both sensory-visual processes in a P110 micro-state and cognitive-linguistic processes in an early N400 micro-state were affected in dyslexic children, and processing delays, as well as qualitatively different patterns of neural activation, were found. Our findings also indicated that the use of specific cognitive tasks and of appropriate spatio-temporal analyses of event-related map series are critical factors for successful identification of specific processing deficits in brain mapping studies.

Adolescent↗